1. Field of the Invention
This invention relates generally to compasses, and more particularly, to an adjustable magnetic compass for adjustably compensating for the magnetic variation between magnetic north and map north.
2. Background Art
Compasses, and more particularly magnetic compasses for use in finding direction, have been known in the art for many, many years. Indeed, one example of such a prior art compass comprises a float-type magnetic compass having a compass dial with indicia representative of the north, south, east and west directions, as well as compass points therebetween, operatively disposed on the face of the compass dial. The compass dial is attached to a two-pole magnet which is pivoted about a vertical axis with its poles in the horizontal plane. Accordingly, the magnet will align itself with magnetic north--which differs from true north by the variation angle.
Such prior art magnetic compasses further include a stationary lubber line associated with the indicia on the compass dial. Accordingly, the specific indicia which aligns closest with the lubber line serves to indicate the directional positioning of the compass with respect to magnetic north.
Although such prior art compasses have been relatively accurate with respect to identifying the directional positioning of the compass with respect to magnetic north, they have been deficient with respect to properly identify true, or map north. For example, many of such magnetic float-type compasses have been used in automobiles for purposes of identifying the direction of travel of the vehicle. However, the directional layout of streets in most major cities, and more particularly the directional layout of north bound streets, are typically based on true north, as opposed to magnetic north. Accordingly, unless the magnetic compass is to be used within a city whose longitudinal positioning is substantially in-line with respect to both true north and magnetic north, the compass will not accurately reflect the direction of travel of the vehicle--with respect to true north.